A switched-inductor power converter is the most widely used DC-DC power converter topology in power electronics due to its high efficiency and power-handling ability. A Buck DC-DC power converter can be used to step down voltage from its input/supply to its output/load. Thus Buck converters are also referred to as step-down converters. In a Buck converter, an inductor is used to store energy and two switches are used to control the currents flowing in the inductors.
It is desirable for DC-DC power converters to work at high voltages (e.g., greater than 20 volts (V), high power density, and high frequencies (e.g., greater than 10 megahertz (MHz)), while at the same time, achieve high levels of integration for efficient power delivery and fast transient response. Currently, the switches for DC-DC power converter are usually silicon-devices, e.g., complementary metal-oxide semiconductor (CMOS) for low voltage (e.g., less than 5V) and discrete silicon (Si)-trench devices for higher voltage (up to 50V). However, Si devices have high on-resistance (Ron) and gate capacitance (Cg), and therefore it is challenging for these devices to achieve high switching frequency and high power density. At the same time, low frequency requires larger passive devices (e.g., inductors), the consequences of which are larger converter size and slow transient response.
High-electron-mobility-transistors (HEMTs), such as gallium nitride (GaN) transistors, have high breakdown voltage, low on-resistance, and high operation temperature, which makes them ideal candidates to replace silicon switches for high power, high voltage Buck converters. Meanwhile, on-chip magnetic inductors (closed yoke inductors or solenoidal inductors) can provide the dense energy storage required for integrated power converters to achieve the high level integration for high efficiency power delivery and fast transient response.
Currently, the GaN-switch-based power converters use discrete parts, such as a GaN switch chip, a Si CMOS chip and discrete inductors, then all the parts assembled on a printed circuit Board. This non-integrated structure has a big size, has large parasitics, limited switching frequency, and low efficiency.
Thus, integrated power converter designs would be desirable.